Extended Data Fig. 1: Quantifying the medio-apical F-Actin dynamics.
a, Comparison between live (eGFP::UtrCH) and fixed (Phalloidin) F-Actin localization in ectodermal (GBE) and amnioserosa cells (DC). b, Automatic cell segmentation procedure used to define medio-apical ROIs for quantification (see Methods). Briefly, cell boundaries are detected on the lower junctional plane using a watershed algorithm. The segmented cells are then identified and tracked over time to define ROIs. Finally, these ROIs are shrunk of a few pixels to discard the junctional signal and the medial fluorescence intensities are measured on the max. proj. of the Z-series. c, Presentation of the background subtraction procedure (see Methods). The background is evaluated on the lower Z-planes and subtracted from the max. proj. of the Z-series before quantification. Removing the background is critical to properly measure the total amount of fluorescence in the ever-changing apical cell surface (see time shift when comparing the medial F-Actin levels with or without background subtraction). d, To quantify the levels of pulsed contractility, we processed single cell profiles using a high-pass Butterworth IIR filter (see Methods). This filter is used to remove low frequency components and have been adjusted to fit the temporality of pulsatility in GBE and DC. Results in a,c,d have been systematically observed in 20 independent experiments. Scale bars size is directly indicated on the pictures. Statistical source data are provided in Source Data Extended Data Fig. 1.
